First-principles simulations of liquid silica : Structural and dynamical behavior at high pressure
By Bijaya B. Karki, D. Bhattarai, L. Stixrude. 2007
145 citations recorded by the source corpus.
We have carried out first-principles molecular dynamics simulations of silica liquid over a wide range of pressure (from $0\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}\ensuremath{\sim}150\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$) and temperature $(3000\char21{}6000\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ within density functional theory and the pseudopotential approximation. Our results show that the liquid structure is highly sensitive to compression: the average Si-O coordination number increases from 4 at zero pressure initially slowly on compression and then more rapidly after 30% compression, reaching 6.5 at $150\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. At low compression, nearly all Si-O coordination environments are fourfold and relatively undistorted, whereas at high compression several coordination types (five-, six-, and sevenfold) coexist and the polyhedra are significantly distorted. The heat capacity and Gr\"uneisen parameter show little variation with compression within the low-pressure regime and vary rapidly with compression in the high-pressure regime. Results are successfully fitted to the Mie-Gr\"uneisen equation of state and show no evidence of spinodal instability or a temperature of maximum density. The behavior of the self-diffusion coefficient is consistent with a crossover from strong to fragile liquid behavior with increasing temperature and increasing pressure. Both Si and O self-diffusion coefficients vary anomalously at $4000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$\char22{}they initially increase with pressure and then decrease upon further compression. This anomalous behavior is absent at higher temperatures.
Subfields: Ceramics and Composites, Geophysics, Materials Chemistry
View Paper: https://www.semanticscholar.org/paper/95e9ca8fe361932b999df5b249c97cd3c5963fef
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In Ceramics and Composites
In Geophysics
- L. Stixrude
- Nico de Koker
- Bijaya B. Karki
- C. Lithgow‐Bertelloni
- S. Karato
- Paul J. Tackley
- J. A. Connolly
- Mark D. Behn
In Materials Chemistry
Citations in the corpus
- Thermodynamics, structure, dynamics, and freezing of Mg2SiO4 liquid at high pressure (2008, methodology): “Self-diffusion coefficients increase with temperature and decrease with pressure (Fig. 12), and do not show the initial increase with increasing pressure seen in more highly polymerized silicate liquids (Angell et al., 1982; Karki et al., 2007 ): The pressure and temperature dependence is well desc”
- Thermodynamics of silicate liquids in the deep Earth (Invited) (2009, background): “Subsequently, we have found that γ increases on compression in other compositions as well, so that this is likely a universal feature of silicate liquids (de Koker et al., 2008; Karki et al., 2007; Mookherjee et al., 2008).”